Plio-Pleistocene valley incision in the Eastern Alps

The project reconstructs the history of valley incision in the Eastern Alps. Information about the incision is gathered in caves. The level of transition between the vadose zone and phreatic tubes in karst caves depends on the spring. A connection between springs and valley bottoms develops if the situation is undisturbed from lithological or tectonical inhomogenities. If the valley bottom is lowered, the caves adapt to the next lower level. Cave morphology and cave sediments together deliver information about when the cave was active, phreatic, drowned, or infilled again. Relative chronologies of erosional and depositional events are developed and permit relative ages of both the deposits and the cave. Cave sediments are dated by the use of cosmogenic isotopes (10Be and 26Al). Sediment at the surface is irradiated by cosmic rays and produces cosmogenic nuclides in a fixed ratio. Once the sediment is washed underground, the two isotopes decay differentially, and the ratio changes. Measurement of the isotope ratio therefore indicates the time since the sediment is underground. This method is called Burial Age Dating. It is a reliable tool to get ages up to 5 Ma, thus covering the whole Pliocene and Pleistocene. From the documented valley lowering in time, valley lowering rates are deduced. In the project, caves on the northern side (mainly in the Salzburg area) and southern margin (Slovenian caves) of the Alps are investigated. The obtained data is compared with other areas of the Alpine arc.